Orbits with Gravity Lab Software

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For centuries, humankind has sought to find order in the universe. In the context of Western thought, in any case, beginning with the Egyptians, Persians, ancient Greeks; in the Americas the Mayans and Azteks, Astronomy evolved out of the necessity to discover a reliable predictor of the seasons for the purposes of agriculture. In most cases, Astronomy takes on a spiritual role in culture as well. The system of accounting that ancient peoples used to measure the seasons evolved, after a great amount of suffering and turmoil, into the physics of Gallileo and the mechanics of Newton. And Newton's remarkable system is still used today, so long as the velocities are not close to the speed of light and the mass vs. density ratio of massive objects is not too great. Linked above is a gravitational simulator upon which several models of celestial motion are explored.

Written in the simple computer language of Q-Basic 4.5, the software is compilable on native systems. At the core is code that generates six n-dimensional arrays. The six arrays correspond to variable requirements in 2-d space, they are velocity vector (in polar coordinates), velocity magnitude, mass, radius, x-position, y-position. "n" corresponds to the number of total objects in the system. Once data is gathered, either entered by hand, loaded from a file, or generated randomly, the simulation can begin. There are three major divisions of the simulation, corresponding to object selection, object position change, and object velocity change, where the actual physics takes place. The simulation begins with object 1, with initial velocity vo, and calculates the next change in velocity of object 1 from the acceleration generated by all other objects. From the gravitational acceleration of object 2, for example, a new velocity vector for object 1 can be determined, and refined until object n's effect on object 1 is considered. The sim goes down the line to object n, correcting the current velocity magnitude and vector until all acceleration effects are accounted for for all objects, then the sim erases the current position of all objects, displaces the objects dependant on their current (freshly calculated) velocities, redraws them, and returns to calculating new accelerations. The result is a fairly accurate model of gravitational motion, in which the orbital properties discussed in mechanics can be seen. Inaccuracies result with high velocities or close interactions (no collision detection is made).

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